Machine-switching telephone-exchange system



' R. L; STOKELY I MACHINE SWITCHING-TELEPHONE EXCHANGE SYSTEM.

Fil pril 20. 1-92 4 Sheet-Sheet 1 [04.3v MARGINAL Jmfiy 15 1924.-

R. L. STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM 9y W R a m R. L. STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM Filed April 20 1921 4 Sheets-Sheet 3 9m, W A mm m M. Fr 7 mm w Nun v L h w Eh v, R Li a a R E E Q b M 3m \QSKEQ mm obn U 1 QM hwm 3m, pg

juiy 15. 1924.-

R. L. STOKELY MACHINE SWITCHING TELEPHONE EXCHANGE sYsrrEM 4 Sheets-She 4 Filed April 20. 1921 Patented July 15, 1924.

UNITED STATES PATENT OFFICE.

RAY L1. s'roxnny', or FLORAL rank; new; ISLAND,- NEW YORK, AssIeNoR TowEs'r- ERN anaemic COMPANY, moonrcmwnn, on NEW YORK, N. Y., A CORPORATION 61* New YORK.

MA-cHiNE-stvrrcHINe TELEPHONE-EXCHANGE SYSTEM;

Application filed A- rn 20, 1921. Serial No. 462,868.

To gi-ZZ whom it may concern: a

,Be it known that I, RAY L. SirOKELY', a citizen of the United States of America, residing at Floral Park, Long Island, in the ceiiiity of Nassau, Stateof New York, have i invented certain new and useful Improve niefits in Machine-Swit hing Tele hone-Exchange Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone ,eX-

change systems employing machine switching and its object is to proyide an iinproVedpcir- 'c'iiit arrangement to take care of toll calls to and from full aiitematic o'fiices'.

This invention is an improvement upon the syetemshown and described in my application. filed July 26, 1919, Serial No. 313,521 for telephone exchange system.

In the system of that application the signal device ferindicating that all trunks are busy is located in the c'ordc'ircuit, and i's'no't actuated nritil the toll operator resteres her dialing key after having dialed all digits of the Wanted number, even though the first selector of the series found the desired trunk group busy.

In the present arrangement such device operates as soon as any selector encounters a busy trunk group Where'upon the operator knows that itis useless to transmit any more digits of theca lled number. She therefore abandons the attempt to establish the conneetionuntil'latein i c 1 Another feature of this invention is the provision of a circuit arrangement comprising relays only, for automatically connectiiig the toll op'erators dial to the selected trunk merely upon the insertion of the plug iii the jack of such tiiin'k; which requires no other act on the part of the dp-eratomheidle condition [of the called line causing a circan change to automatically disconnect the dial freni such trunk, and to connect the tiun'jk througli' to the cord used. Y

Still another feature is the provision of a cir'ciiit arrangement whereby if the 'con nectoi finds the selected line busy the dialis also automatically disconnected from the trunk and the circuit connected through to the supervisory relay in the cord circuit which relay is intermittently operated from an interrupter connected to the trunk due to the busy condition of the called line thereby flashing the calling supervisory lamp as a busy signal to the. toll operator.

Referring to the drawings; Fig. 1 shows a toll cord circuit and part of a trunk outgoing from the toll board to a full mechanical or automatic office; Fig. 2 shows an incoming elector at the full mechanical ofiice; Fig.3 shows a toll transmission selector repeater; Fig. 4: shows a combination toll and local connector. I

The invention will be most readily understood from a description of the operation of the system. I

The toll operator having, been informed, for example, by the recording operator, of the number of the Wanted line in the automatic oflicc, tests foran idle trunk by touching the tip other plug 100 to the sleeve of the jack 101' of the toll switching trunkand if she does not heara click in her head set connected to the tip through anormal contact or re1ay 102 inserts the plug into the jack. The sleeve of the plug applies potential to the sleeveof the jack to cause the seized trunk tote's t busy at the other toll operato'rstpositions, Relay 102 operates in series with relay F, disceiinects the operators head set and connects the tip of the plug through to the bridged calling supery-isor'y relay 103. Relay 104 is marginal and operates only when the plug is inserted into the jack of a toll linfeleading to a distant toll switchboard and under such circumstances cuts foffthe bridge Containing relay 103 to prevent this bridge from shunting the alternating current applied by the operator at such distant toll switchboard to operate an z t-lternatiiigcurrent l elay, (not shown) in the cord circuit. This is in accordance with well known practice. Relay F in attracting its inner right armature locks itself in series with relay C and in attracting. its outer right armature operates relay G. Relay G locks itself in a circuit including the armature and normal contact of relay J, and operates relay H to open the bridge containiiig relay J. Relay G at its right armature's interconnects the incoming and outgoing, ends of the trunk and relay F at its outer and middle left armatures connects the impulse contact 106 of the toll operators dial 105 through relays D and E to the impulse relay A of the incoming selector at the distant automatic office. The dial is common to the trunks of the position. Relays A and .D operate in this circuit, but relay E is polarized and does not respond to this direction of current flow. Relay D in closing its contact operates relay B which at its inner armature interposes a break in the circuit of lamp 107. Thislamp will light only when one of the selectors encounters a busy trunk group. Relay B at its right armature closes a shunt around the right armature contact of relayA. Relay A operates the usual slow relay B which opens the circuit of the release magnet 240 and connects the vertical magnet 210 to the back contact of the impulse relay A in the well-known manner.

When the operator rotates the dial for the first digit contact 108 closes, operating relay A which in attracting its inner armature locks itself to the front contact of relay C and in attracting its outer armature provides a circuit to hold relay B operated while the armature of relay D is vibrating as the dial restores. Dial 105, in returning to normal, interrupts at its impulse contact 106 the circuit of the impulse relay A Upon each retraction of the armature of relay A the following circuit is closedfor the vertical magnet 210 of the incoming selector: grounded armature 211, and back contact of relay D "conductor 212, armature and back contact of relay A lower armature and front contact of relay B slow relay C vertical magnet 210, and free pole of battery. On the first step of the selector, off normal springs 213 close the following circuit for relay 214: free pole of battery, relay 214, conductor 215, off normal springs 213, conductors 216, 217, armature and front contact of relay C to ground at the upperarmature and front contact of relayB Belay 214 in attracting its upper armature locks itself over the following circuit: free pole of battery, relay 214,conductor 215, off normal contact 213, conductor 216, armature and back contact of rotary magnet 218, conductor 219, upper armature and front contact of relay 214, to ground at the armature 211 and back contact of relay D Upon the cessation of the impulses relay A remains energized and consequently relay C which is slow to release, after an interval releases, whereupon the following circuit is closed to energize the rotary magnet 218 of the selector to step the selector brushes onto the first trunkin the selected level: free pole of battery, magnet 218, conductor 222, lower armature and front contact of relay 214, upper normal contact of relay C upper. armature and front contact of relay B to ground. 'At the end of its stroke, the rotary magnet 218 opens the locking circuit traced for relay 214. Relay 214 in retracting its lower armature opens the circuit of the rotary magnet. 1f the first trunk is busy, ground is present on the test multiple 223 thereof, whereby the following circuit is closed to again energize relay 214: grounded multiple 223, test brush 224, conductor 225, armature 226 and back contact of relay D conductors 227, 219, back contact and armature of magnet 218, conductor 216, switch 213, conductor 215, relay 214 to free pole of battery. Relay 214 in attracting its upper armature again locks itself through the back contact of the rotary magnet and in attracting its lower armature again closes the circuit of the rotary magnet whereupon the selector brushes are stepped I to the next trunk. This interaction of the relay 214 and the rotary magnet is continued until an idle trunk is found which is indicated by the absence of ground on the test multiple 223 thereof. When the rotary magnet, at the end of its stroke, positions the brushes on this idle trunk, no ground being present, relay 214 does not energize but switching relay D energizes over the following circuit: free poleof battery, relay 214, conductor 215, switch 213, conductor 216, armature andback contact of rotary magnet 218, conductor 219, conductor 227, conductor 228, relay D conductor 229, lower normal contact of switch 207, conductor 230, to ground at the upper armature and front contact of relay B Relay 214 is marginal and does not operate in this circuit. Relay D in attracting its armatures 204 and 201 extends the talking conductors 7 through to the selector brushes and cuts off impulse relay A Assuming now that the selector has failed to find an idle trunk, on the eleventh rotary step, switch 207 is operated by the shaft of the selector and at its upper contacts opens the circuit of the impulse relay A which causes the selector 2) to restore. The opening of the loop circuit also causesrelay D (Fig. 1) to be permanently deenergized.

'VVhen the dial reaches its normal position after being rotated for the first digit the contact 108 opens one of the circuits traced which circuits have been holding relay B energized and relay D being inert the other circuit for relay B is also open. Relay B thereupon releases, the retraction of its inner armature closing the circuit of lamp 107. This circuit includes the front contact of relay 6. The toll operator knows by the illumination of this lamp that the incoming selector has failed to find an idle trunk. If she fails to notice the lighted lamp and operates the dial for the rest of the digits, this has no effect on the switches because the impulse circuit is open atthe right armatures being locked in a circuit including the front contact of relay C. If it were-not for this arrangement the impulses of the second dig it would operate the incoming selector and the rest of the digits would operate succeedin'g switches which would either result in a false connection or useless operation of the switches. Upon noticing the lighted lamp, the operator removes the plug from the jack, releasing the relays F, C, H, and A. Relay G is unlocked when relay J operates in series with relayA of the incoming selector when the off-normal switch 207 is closed as such selector reaches its normal position.

'Assurning, however, that an idle trunk was found,- the seizure of the toll transmission selector repeater Fig. 3, in which such trunk terminates, causes the closure of the follox'ying circuit for impulse relay A thereat, free pole of battery, left hand winding of relay A conductor 300, contact 301, of relay 3*, conductor 302, contact 303 of relay F, conductor 309, lower left hand winding ofrepeating coil 30 4, conductor 303, multiple terminal234, brush 233, conductor 232-, armature 201 and front contact of relay D conductors 202, 109, inner ri ht armature and alternate contact of relay (x, conductors 110, 111, middle left armature and alternate contact of relay F, relays E and D, impulse spring 106, conductor 112,.outer left armature and alternate contact of relay F, conductors 113, 114, outer right armature and alternate contact of relay G, conductors 115, 203, armature 204 and alternate contact of relay D conductor 252, brush 250, multiple 251, conductor 307, upper left winding of the repeating coil, conductor305, contact 306 of relay F conductor 310, contact 311 of relay B conductor 312, left winding of relay A switch 313 operated only-on the eleventh rotary step of the selector, to ground. The impulse relay A in attracting its right armature e'nergizes slow relay 314. This relay in attracting its outer left ari'n'ature supplies a ground to the test multiples 223 to cause this trunk to test busy. hen the relay 314 operates it closes at its right hand armature the following circuit for relay D ground, right armature and front contact'of relay 314, conductors 315 and 316, contact 3170f relay G conductor 318, outer right hand armature and back contact of relay F conductor 319, relay D to free pole of battery.

The second operation of the dial by the operator transmits the corresponding digit of the called line causing relay A to transmit impulses over the following circuit to the Vertical magnet 320 of the selector re- 'peater: ground, right armature and back contact of relay A inner left armature and front contact of relay 314, conductor 321, armature 322, and back contact of relay G, conductor 323, slow relay 324, magnet 320 to free pole of battery. The brushes of the selector are thus elevated to the desired level. When the dial returns to normal and maintains the relay A energized after a slight interval, slow relay 324 releases. l ihen the relay 324 ope-rated on the first impulse and the selector took its first step, relay 325 corresponding to relay 214 2) operated over the following circuit: free pole of battery, relay 325, upper contact of off normal switch 325, conductor 327 armature and front contact of relay324, conductor 390,- armature 329 and back contact of relay 330 to ground. In attracting its inner armature, relay 325 looks itself, this circuit including the armature and back contact of rotary magnet 331. These circuits are similar to those of the selector of Fig. 2. Upon the cessation of the impulses and the release of the slow relay 324, the circuit of the rotary magnet is closed as follows: free pole of battery, magnet 331, outer armature and front contact of relay 325, normal contact of relay 324, conductor 390, to ground at the armature 329 of slow relay 330. The rotary magnet advances the brushes onto the terminals of the first trunk and at the end of its stroke opens the locking circuit of the relay 325 which releases opening the circuit of the rotary magnet. If the trunk is busy, relay 325 again energizes over the following circuit: free pole of battery, relay 325, upper contact of switch 326, conductor 327, armature and back contact of rotary magnet 331, conductor 333, back contactand armature 334 of relay G conductor 335, armature 336 and back contact of relay 330, conductor 337, test brush 338 to ground on the test multiple 339. Re-

lay 325 in attracting its inner armature again locks up and at its other armature again closes the circuit of the rotary magnet which advances the brushes to the next trunk and at the end of its stroke opens the locking circuit of relay 325 which in re tracting its armature opens the circuit of the rotary magnet 331. The switch 313 corresponds to the switch 207 of the incoming selector circuit, Fig. 2. Its function is to permanently open the circuit of the impulse relay A on the eleventh rotary stop of the selector, that is to say, if all the trunks in the group are busy. The opening of this circuit releases slow relay 314 which in retracting its outer left armature releases relay D of the incoming selector. Relay D in retracting its armature 211 effects the operation of release magnet 240 whereupon the incoming selector switch is restored to normal. Relay 314, in retracting its inner left hand armature. closes a circuit for re lease magnet 383 whereupon the selector repeater (Fig. 3) releases. In releasing its armature 201, relay D opens the circuit for relay D (Fig. 1) whereupon the all trunk busy lamp 107 (Fig. 1) is illuminated as previously described. If, however, an idle trunk is found, relay G which corresponds to relay D Fig. 2 operates over the following circuit: free pole of battery, relay 325, upper contact of switch 326, conductor 327 armature and back contact of magnet 331, conductor 333, relay G conductor 340, upper contact of switch 313, conductors 341, 315, to ground at the right armature and front contact of relay 314. Relay is marginal and does not operate in this circuit in series with the relay G Relay G operates and in attracting its armatures 342 and 343 extends the talking conductors through to the talking brushes 344 and 345. The attraction of the armature 334 of relay G grounds the test brush 338 and consequently test multiples 339 of the selected trunk, causing the same to test busy to other selectors. The contact 346 is made before the contact 317 is broken by the armature 347 of the relay G Consequently relay D is maintained energized over the following circuit: free pole of battery, relay D conductor 319, outer right armature and back contact of relay F conductor 318, contact 346, armature 347, conductor 348, brush 349, multiple 350, control conductors 351, 400, (Fig. 4), conduct-or '1, armature 402 and back contact of relay K conductor 403, sleeve conductor 450, conductor 352, multiple 339, brush 338, conduotor337, armature and back contact 336 of relay 330, conductor 335, armature 334 and front contact of relay G conductor 315, to ground at the rightarmature' and front contact of slow relay 314. Thus, the circuit for relay D (Fig. 3) is maintained closed as the circuit is extended. The switch of Fig. 4 to which the connection has been extended is a combination toll and local connector containing multiples of ordinary automatic. subscribers lines in its bank. This switch is accessible not only to the selector-repeaters of Fig. 3, but also to the local selectors which are used by the subscribers in building up their own connections. The seizure of the connector causes the closing of the following circuit for the impulse relay A free pole of battery, upper winding of relay A conductor 404, contact 475 of relay D conductor 405, left winding of slow relay J, conductor 407, lowermost armature and back contact of relay K ring conductor 446, conductor multiple 354, brush 345, conductor 355. armature 343 and front contact of relay G left armature and front contact of relay A, ring conductor 357, armature 356 and back contact of relay H conductor 358, lower right hand winding of the repeating coil 304, resistance 359, conductor 360, inner left armature and front contact of relay D left winding of relay 361, conductors 362, 363, resistance 364, upper right hand winding of repeating coil 304, conductor 365, upper armature and back contact of relay H uppermost armature and front contact of relay G brush 344, multiple 367, tip conductor 410, upper armature and back contact of relay K conductor 476, back contact 477 of D*, lower winding of relay A to ground. lVhen relay G (Fig. 3) operates a circuit is also closed through the right hand winding of relay 361 which leads over 376, 370, armature 334 and front contact of G conductor 315, to ground at the armature and front contact of relay 314. The current in the circuit just traced is opposite in direction to that in the left hand winding of this relay. Consequently this relay does not operate at this time. Relays J and A operate, however, the former atits innermostright armature closing a locking circuit for itself as follows: free pole of battery, right winding and right innermost armature and front contact of J conductor 431, conductor 415, to ground at the armature 416, and front contact of slow rela B which is ener ized upon the energization of the impulse relay A Relay B grounds the sleeve wire 41-7, leading to the test multiples in the local selectors, this circuit leading from grounded armature 416, conductor 415, to conductor 417.

The return of the dial to normal in transmitting the tens digit of the wanted number interrupts the circuit of relay A, which in vibrating its armatures transmits im-- pulses to the vertical magnet 418 of the connector. The circuit for the first impulse is as follows: free pole of battery, magnet 418, slow relay 419, right contact of off normal switch 420, conductor 421, lower armature and front contact of relay B to ground at the armature and back contact of the im pulse relay A At the first step of the connector, the off normal springs 420 are shifted and the succeeding impulses are transmitted by way of the upper armature and front contact of relay 419 and the contact 422 now closed at the off normal springs 420. Relay ll is operated by its lower winding when relay 419 operates, this circuit in cluding the innermost right armature of relay J and grounded armature 416 of relay B Relay F locks up to the sleeve wire 450 in a circuit including armature 402. The connector brushes are thus lifted to the desired level and upon the cessation of the impulses, impulse relay A. remains energized and relay 419 in series with the vertical magnet releases preparing the circuit of the rotary magnet 423. The units impulses pass through the back contact of the impulse relay A, lower armature and front contact of relay B conductor 421, off normal contact 422, back contact of slow relay 419, conductor 424, innermost left armature and front contact of relay G, conductor 425-, uppermost armature and back contact of relay H rotary magnet 423 to free pole of battery. The connector is thus stepped around into engagement with the desired line.

If this line is idle, full potential is present onitstest multiple 426 through the cut oil winding of the line switch, and the following circuit is closed to operate relay H multiple 426, brush 4:27, conductor e28, armature 4A0 and back contact of relay E, conductor e29, upper winding of relay H conductor 430, right hand armature and back contact of relayG, conductor 4:31, conductor 415, armature 416 of relay B to ground. Relay H in attracting. its arma ture 532 looks itself to the grounded sleeve wire 450 and extends this grounded conductor over conductor .133, middle right armature and front contact of relay J conductor 434 to the relay K Relay K in attracting its armature 402 disconnects the grounded sleeve wire 450 from the control lead 400 leading back to the relay D Fig. 3 of the selector repeater. Relay D in,re tracting its outer l ft hand armature operates relay F, to reverse the current flow in the circuit leading back to the operators cord to energize relay 103 tolight the lamp 117 (Fig. 1) as a ringing signal to the toll operator. The circuit for relay F is as follows: free pole of battery, relay F conductor 369, outer left armature and back contactof relay D conductor 370, armature and front contact of relay G conductor 315 to ground at the right armature and front contact of relay 314. Relay F" in attracting its outer right armature applies the following substitute ground to hold up the relay F before it can release in order to prevent ringing from occurring at this time as would occur if this relay released: ground, left hand armature and back of relay 371, conductor 37 2, outer left armature and back contact of relay B outer right armature and front contact of relay F control conductor 318, contact 34:6 and armature 347 of relay G conductor 348, brush 349, multiple 350, conductor 351, conductor a 00, front contact and armature 435 and lower winding of relay F to free pole of battery. The operation of relay K by releasing D and operating F which caused the reversal of direction of the on rent flow in the loop leading back to the toll operators position opens the locking circuit of relay F and unless a substitute circuit is provided for holding up relay F as just de scribed, afterrelay K operates the ringing operation would automatically take place as will appear. This is prevented by applying ground to the control conductor 400 over the circuit traced to hold the relay F until the operator,'by depressing a key as --will be explained, releases relay F to start the automatic ringing operation. The release of the relay D and the consequent energization of relay F as described reverses the direction of current flow in the talking conductors leading back to the operators position. This reversal operates polarized relay E (Fig. 1) which releases elays F and G which in deenergizing disconnects the dial from the trunk 110, 114; and connects the trunk through to the calling supervisory relay 103 whichnow operates in series with the impulse relay A 1 of the connectorf Relay 103 in operating lights the calling supervisory lamp 117 as a signal to the toll operator that the line desired was found idle by the connector. Relay F also releases relay D. Relay A unlocked when relay C released. Relays E. C, D, A. and B are individual to the dial and common to the trunks at a position.

Relays F, J, H and G are individual to a given trunk. ringing key RK which impresses alternating current upon the talking conductors which operates the alternating current relay C which in attracting its armature 0perates the relay 371. This relay in attracting its left armature opens the circuit heretofore traced, which has been holding relay F Fig. 4, energized. This relay in retracting its arinatures 37, 499 connects ringing current to the called line through its upper winding. This ringing current is automatically intermittently applied until the called party removes his receiver, resulting inan increase in the current through the upper winding of relayF causing the same to' operate removing the ringing current. The attraction of the armature 435 of this relay closes a locking circuit for the same over grounded control conductor 4:00. The extension of the tip and ring conductors by relay F to the called line operates relay 373 over which talking current is fed to the called line. Relay 373 in operating energizes relay B which in attracting its outer left hand armature applies ground to the conductor 374, and outer right armature of relay F conductor 318, contact 346,

The operator now operates the supervisory lamp 117 which notifies the operator that the subscriber has responded. Talking current is fed to the called line over the winding of relay 373 and the repeating coil 304. This talking circuit is a stand ard repeating coil transmission circuit used in long distance connections. Talking current is fed to the calling line from the distant exchange. trunk leading from the left hand windings of repeating coil 304 through the right hand winding of the repeating coil (not shown) at the distant office, is dry, in accordance with standard practice.

Assuming now that the desired line when selected by the connector is busy, the test multiple 426, Fig. 4, is grounded. When test wiper 427 is set on the busy multiple 426, ground is extended over brush 427, conductor 428, armature 440, contact 444 of relay E, conductor 441, armature 442 and back contact of relay H conductor 443, relay G to free pole of battery. Relay Gr energizes and when slow relay E releases, locks itself up over the following cir cuit: free pole of battery, relay G, conductor 443, armature 442 and back contact of relay H conductor 441, make before break contact 498 of relay E right armature and front contact of relay G, conductor 431, conductor 415 to ground at the armature 416 and front contact of relay B Relay G in the case of a local call connects busy tone from the source 445 to the calling line. In the case of a toll call this busy tone is not used, a flashing signal being given to the operator instead. Relay G in operating due to the line being busy prevents test relay H from operating when slow relay E releases. When busy test relay G operates a circuit is closed for relay D from free pole of battery, upper winding of D, conductor 478, conductor 479, contact 480 of relay K, conductor 481, resistance 490, armature 482 and back con.- tact of relay E outer left armature and front contact of G inner right armature of relay J and front contact, conductor 431, 415 to ground at armature 416 and front contact of B Relay D reverses the direction of current flow through the left winding of relay 361 (Fig. 3) which results in this relay operating. The left armature and front contact of relay 361 closes a circuit for operating relay F as follows: battery. relay F conductor 369, left armature and. fi ont contact of relay 361, conductors 376, 370, armature 334 and front contact of G conductor 315 to ground on the right armature and front contact of relay 314. Relay F reverses the direction of current flow in the circuit leading back to the operators cord as in the case of an idle line to operate polarized relay E whichin turn releases relay F to connect the talking conductors of During conversation the the cord through to the connector and also releases the common relays E, C, D and A as in the case of. a free line. The right armature of relay 361 connects interrupter 379 to relay 371 which in operating intermittently applies ground to conductor 300 in shunt of the circuit leading over tip conductor 307 back to the operators cord. The circuit of relay 371 leads over the outer right back contact of relay D to ground at the right armature of relay C The inter mittent ground applied to conductor 300 by relay 371 shunts out the relay 103 intermittently which causes the flashing of the lamp 117. The operator thus knows that the desired line is busy and removes the plug from the trunk switching jack. This causes the release of all switches and the return to normal condition of all the apparatus including the various locked up relays.

During the conversation the called sub scriber by moving his hook up and down causes the supervisory lamp 117 at the toll operators position to flash as in the case of manual telephone exchange practice, without releasing the switches. This is apparent from the pregeding description inasmuch as relay 373 is in circuit with the called line and each time it attracts its armature operates the relay B which removes battery and ground from the trunk conductors leading back to the supervisory relay 103 and places a bridge across the relay A to hold it operated to prevent release of the switches. \Vhen the called subscriber replaces his receiver the lamp 117 lights at the toll operators position, Fig. 1.

The operator may rering the subscriber after he has replaced his receiver if she desires to recall him by actuating her ringing key RK, which operatesrelay C to operate 371 which in attracting its left hand armature again releases relay F which initiates the automatic ringing operation at the conneitor. The control of this relay F was removed from the relay 371 by the attraction of the outer left armature of relay B when the called subscriber responded and was restored to the relay 371 and consequently to the operator when the called subscriber replaces the receiver and deenergizes relay B \Vhen the operator desires to break down the connection after the called subscriber has replaced his receiver, she removes the plug from the toll switching jack. This releases relay A', Fig. 3, which causes the restorationof all the switches. If, however, the operator removes the plug while the called subscriber still has his receiver off the switch hook, the switches are not released since relay A which controls the release is maintained energized. over the following circuit: battery, left hand winding of relay A conductor 300, armature 380 and front contact of B resistance 381, cond-uctor 312, right hand winding of relay A to ground at the lower normal contact of switch 313, it being noted that the relay B which controls this loop circuit is itself controlled by relay 373 in circuit with the called line and controlled at the switch hook of said line.

The withdrawal of the plug before the called'party has restored his receiver disconnects the battery supplied through relay 102 and the sleeve of the plug from the sleeve multiples of the jacks of this trunk at the other toll positions but relays J, G and H cooperate to place potential thereon in the following manner: when the plug was inserted in the jack and relay F operated, it closed a circuit to operate relay G as described. Relay G then locked itself to battery at the right armature of relay J. Relay J is inert at this time since relay H operated when relays F and G operated. Relay H at its left armature opened the circuit of relay J to prevent the bridge including said relay from interfering with the impulses to the switch. After relay F is released due to relay E operating when the called party answers, relay H is held operated from batteryon the sleeves of the plug and jack to hold open the bridge containing relay J. Nhen however the plug is removed while the calling party still has his receiver ofi' the switchhook relay H releases and relay J being inert due to the trunk 115, 109 being dry, relay G is held locked to battery at the right armature of relay J Battery is thus supplied overthe following path to the sleeves of the jacks: i-ight armature and back contact of relay J, innermost leftarmature and front contact of relay G, conductors 118, 119, right armature and back contact of relay H, resistance 120, middle left armature and front contact of relay Gr, conductor 121, innermost left armature and back contact of relay F, conductor 122 to the sleeve multiples. Relay G is locked in a circuit including the same armature of relay J. When the called party replag'es his receiver battery is applied to the trunk 115, 1.09 as described and relay J operates, unlocking relay G thus removing the busy condition from the jacks of this trunk at all the toll positions at which they appear. I

'Assuming, however, that the called subscriber has replaced his receiver, when the operator removes the plug, relay A in releasing deenergizes slow relay 314. Relay 314 in retracting its outer left armature removes ground from the sleeve conductor 382 leading to the release relay ID whereupon this relay closes the circuit of release magnet 240 as follows: free pole of battery, magnet 240, off normal switch contact 213, lower armatures and back contacts of relay B and A to ground at the armature 211 and back contact of relay D Thus the first. selector is restored and upon reaching its normal position opens the OE normal springs 213. The removal of ground from conductor 315, by the retraction of right hand armature of relay 314 releases relay G and the retraction of the right hand armature of relay A and inner left armature of relay 314 closes a circuit for the release magnet 383 at the selector repeater. The slow relay 330 is energized in parallel with the release magnet and opens the circuit to the test brush 338 during restoration at its armature 336, to prevent interference with other connections. At its armature 38 1 it short circuits the right hand winding of relay A At its armature 329 it closes a locking circuit for itself which is opened when the off normal switch 326 assumes its normal position. The opening of the circuit of the tip and ring conductors 410, 4146 causes the release of relays A B J Fig. 4:, which results in the closure of the following circuit for connector release magnet 440: free pole of battery, magnet 440, left hand contact of ofi normal switch 420, back contact and'lowermost armature 183 of relay 1), the lower armature and back contact of relay B and A to ground. The connector upon reaching normal position restores the off normal switch 420.

What is claimed is:

1. In a telephone system, the combination with telephone lines, an operators position, trunks terminating thereat in jacks and at the other end in selectors, other antomatic switches, cord circuits at said position, an impulse sender common to said trunks, electromagnetic means automatically operated by the insertion of a plug of a cord circuit into the jack of a trunk for connecting said impulse sender to said trunk, and electromagnetic means automatically operated by the seizure of the called line irrespective of the busy or idle condition thereof for disconnecting the impulse sender from said trunk.

2. In a telephone system, the combination i with telephone lines, an operators position, trunks terminating thereat in jacks and at the other end in selectors, other automatic switches, cordv circuits at said position, an impulse sender common to said trunks, electromagnetic means automatically operated by the insertion of a plug of a cord circuit into the ack of a trunk for connecting said impulse sender to said trunk, an electromagnetic means automatically operated by the busy condition of the selected line for disconnecting the impulse sender from said trunk.

In a telephone system, the combination with telephone lines, an operators posirzo tion, trunks terminating thereat in jacks and at the other end in selectors, other automatic switches, cord circuits at said position, an impulse sender common to said trunks, electromagnetic means automatically operated by the insertion of a plug of a cord circuit into the ack of a trunk for connecting said impulse sender to said trunk, and electro magnetic means automatically operated by the busy condition of. the selected line for disconnecting the impulse sender from said trunk and for flashing the calling supervisory lamp of the cord circuit.

4. In a telephone system, the combination with telephone lines, an operators position, trunks terminating thereat in jacks and at the other end in selectors, other automatic switches, cord circuits at said position, an impulse sender common to said trunks, electromagnetic means automatically operated by the insertion of a plug of a cord circuit into the ackof a trunk for connecting said impulse sender to said trunk, means actuated by the seizure of the called line for reversing the current flow in the trunk, a polarized relay operated thereby, and means actuated by said polarized relay for disconnecting the impulse sender from the trunk and connecting the called line through to the cord circuit.

5. In a telephone system, the combination with telephone lines, an operators position, trunks terminating thereat in jacks and at the other end in selectors, other automatic switches, cord circuits at said position, an impulse sender common to said trunks, electromagnetic means automatically operated by the insertion of a plug of a cord circuit into the jack of a trunk for connecting said impulse sender to said trunk, means actuated by the busy condition of the called line for reversing the current flow in the trunk, a polarized relay operated, thereby and means actuated by said polarized relay for disconnecting the impulse sender from the trunk and connecting the called line through to the calling supervisory relay in the cord circuit, and means controlled by the busy condition of the called line for flashing the lamp controlled thereby.

6. In a telephone system, the combination with an operators position, trunks terminating thereat in jacks, automatic switches, cordtcircuits at said position, an impulse sender common to said trunks, a relay in each trunk operated by the insertion of the plug in the jack thereof to connect the impulse sender to the trunk, and means for deenergizing said relay automatically operated by the seizure of the called line irre spective of the busy or idle condition thereof to disconnect said impulse sender from said trunk.

7. In a telephone system, the combination with an operators'position, trunks terminating thereat in jacks, automatic switches, cord circuits at said position, an

impulse sender common to said trunks, a relay in each trunk operated by the insertion of the plug in the jack thereof to connect the impulse sender to the trunk, and means for deenergizing said relay automatically operated by the busy condition of the called line to disconnect said impulse sender from said trunk.

8. In a telephone system, the combination with an operators position, trunks terminating thereat in jacks, automatic switches, cord circuits at said position, an impulse sender common to said trunks, a relay in each trunk operated by the insertion of the plug in the jack thereof to connect the impulse sender to the trunk, and means "for deenergizing said relay automatically operated by the seizure of the called line irrespective of the busy or idle condition thereof to disconnect said impulse sender from said trunk and connect said trunk through to the supervisory lamp in the cord circuit.

9. In a telephone system, the combination with an operators position, trunks, terminating thereat in jacks, automatic switches, cord circuits at said position having supervisory relays and lamps associated therewith, an impulse sender common to said trunks, a relay in each trunk operated by the insertion of the plug in the jack thereof to connect the impulse sender to the trunk, and means for deenergizing said relay au tomatically operated by the busy condition of the called line to disconnect said impulse sender from said trunk and connect said trunk through to the supervisory relay of the cord circuit, and means controlled by the busy condition of the called line for connecting an interrupter to said trunk to intermittently operate said relay to flash the supervisory lamp.

10. In a telephone system, the combination with an operators position, trunks terminating thereat in jacks and eatYt-he other end in selectors, an impulse sender common to said'trunks, other automatic switches, groups of trunks terminating therein, electromagnetic means automatically operated by the insertion of a plug of a cord circuit into the jack of a trunk for connecting said impulse sender to said trunk whereby said switches may be controlled over said trunks, a signalling device at said position and means automatically operated when one of said automatic switches encounters a busy trunk group for actuating said signal, ling device. 7

11. In a telephone system, the combination with an operators position, trunks terminating thereat in jacks and at the. other lay automatically operated by the insertion of a plug, of a cord circuit into the jack of a trunk for connecting said impulse sender tosaidtrunk whereby saidswitches may be controlled over said trunks-,1 a lamp at said position-, and meansautomatical ly operated when one of said automatic switches encount'ers' a busy trunk group for lighting said lamp;

12. In a telephone system, the combina ti'on'with an opera-tors position,-trunks terminating thereat in jacks and at the other endin selectors, an impulse sender common t'o said trunks, other automatic switches, groups of trunks terminating. therein, electromagnetic means automatically operated by the insertion ofa plug of a cord circuit into the jack of a trunkfor connecting said impulse sender tosaid trunk-,- a signalling device, arelay operated when said impulse sender is connected to said trunk for opening, the circuit of said signalling device, a second: circuit for holding said relay operatedclosed only when the sender is out of its normal position the loop-circuit including the sender being opened when any solector encountersabusy trunk group whereby suclr relay releases, closing the circuit of said-signalling device. g

13: In a telephone exchange system, the combination with telephone lines automatic switches, groups of trunks, an operators position, a lamp andan impulse'sender common thereto, a relay for automtically connectingythe impulse sender'to a trunk'when the same is taken for use by an operator, and means automatically actuated as soon as any automatic switch encounters a busy trunk group for lighting said lamp-.-

14 In a telephone'exchange system, the combinationwith an automatic oflice, automatic switches thereat, subscribers lines terminating therein, another office, a toll operators position thereat, a lamp at said position, a: cord circuit, a two-wire trunk extending from said position tosaid automatic office, a dial at" said position for setting; the switches at saidautomatic oflice overa circuit including the two sides'of said trunk in series, means for automatically connecting said dial to a trunk in response to the connection of said cord circuit with the trunk, and means automatically actuated as soon as any automatic switch encounters a busy trunk for lighting said lamp.

15. In a telephone exchange system, the combination with an automatic office, subscribers lines terminating therein, auto matic switches thereat, another office, a toll operators position, a lamp thereat, a twowire trunk extending from said position to said automatic office, a dial at said position for setting the switches at said automatic ofiice over the circuit including the two sides of said trunk in series, a cord circuit at said position having a supervisory lamp therein, means automatically actuated upon the seizure of the called line for lighting said supervisory lamp and means automatically actuated as soon as a switch encounters a busy trunk group for lighting said first mentioned lamp.- g

16. In atelephone exchange system, the combination with an automatic oflice, subscribers lines terminating therein, automatic switches thereat, another oilice, a toll operators position, a lamp thereat, a twowire trunk extending from said position to said' automatic office, a dial at saidposition for settingthe switches at said automatic oflice over the circuit including the two sides of said trunk in series, acord circuit at said position having a supervisory lamp therein, means automatically actuated upon the-seizure of the called line for lighting said supervisory lamp, means automatically actuated by the busy condition of the called line for flashing said lamp, and means automatically actuated as soon as any switch encounters a busy trunk group for lighting said first mentioned lamp.

17. In a telephone exchange system, the combination of telephone lines, an operators position, trunks terminating. in selectors, other automatic switches, a connecting circuit at said position, an impulse sender common to said trunks, and means auto matically operated by the connection of a connectingvcircuit to a trunk for connecting said impulse sender to said trunk, and electromagnetic means automatically operated by the seizure of the calledline irrespective of the busy or idle condition thereof for disconnecting the impulse sender from said trunk.

18, In a telephone exchange system, the combination of telephone lines, an operators position, trunks terminating in selectors, other automatic switches, a connecting circuit at said'position, an impulse sender common to said trunks, and means automatically operated by the connection of a connecting circuit to a trunk ior connecting said impulse sender to said trunk, and electromagnetic means automatically operated by the busy condition of the selected line for disconnect-ing the impulse sender from said trunk.

19. In a telephone exchange system, the combination of telephone lines, an operators position, trunks terminating in selectors, other automatic switches, a connecting circuit at said position having a supervisory lamp associated therewith, an impulse sender common to said trunks, and means automatically operated by the connection of a connecting circuit to a trunk for connecting said impulse sender to said trunk, and electromagnetic means automatically operated by the busy condition of the selected line r 1. at terminating in selectors, an impulse sender common to said trunks, other automatic switches, connecting circuits at said position having supervisory relays associated therewith, means automatically operated upon the extension of a connecting circuit to a trunk for connecting the impulse sender to said trunk, electromagnetic means automatically operated by the seizure of the called line for disconnecting the impulse sender from said trunk and for connecting said trunk through to the supervisory relay in the connecting circuit, means controlled by the response of the called party for placing the control of the release of the automatic switches under the joint controlof said called party and the toll operator, and automatically operated by the disconnection of the connecting circuit from the trunk for placing a lousy condition upon the multiples of said trunk at the other positions.

21. In a telephone system, the combination of a toll operators position, trunks thereat terminating in selectors, an impulse sender common to said trunks, other automatic switches, connecting circuits at said position having supervisory relays associated therewith, means automatically operated upon the extension of a connecting circuit to a trunk for connecting the impulse sender to said trunk, electromagnetic means automatically operated by the seizure of the called line for disconnecting the impulse sender from said trunk and for connecting said trunk through to the supervisory relay in the connecting circuit, means controlled by the response of the called party for placing the control oi the release of the automatic switches under the joint control of said called party and the toll operator,

of the receiver by the called party for releasing the automatic switches and for removing said busy condition.

22. In a telephone exchange system, the combination with an automatic ofiice, subscribers lines terminating there-in, automatic switches thereat, another office, a toll operators position, a two-wire trunk extending from said position to said automatic otiice, a dial at said position for setting the switches at said automatic oifice over a circuit including the two sides of said trunk in series, a cord circuit at said position including a supervisory lamp means automatically actuated upon the seizure of the called line for lighting said lamp, a key controlled by the operator for initiating the automatic ringing operation at the last of said switches, means controlled by the response of the called party for cutting off the ringing cur rent and for extinguishing said lamp, means automatically actuated if the called line is busy for flashing said lamp, and means automatically actuated if any selector encounters a busy group for lighting said first mentioned lamp. I I

43. In a telephone exchange system, the combination with an automatic office, subscribers lines terminating therein, automatic switches thereat, another oiiice, a toll operators position, a two-wire trunk extending from said position to said automatic oiiice, a dial at said position for setting the switches at said automatic office over the circuit including the two sides of said trunk in series, a 'cord circuit at said position, a lamp therein, means automatically actuated upon the seizure of the called line for disconnecting said dial, a key controlled by the operator for initiating the automatic ringing operation of the last of said switches, means controlled by the response of the called party for cut-ting ofl the ringing current and extinguishing said lamp, means automatically actuated if the called line is busy "for disconnecting said dial and flashing sa d lamp.

In witness whereof, I hereunto subscribe my name this 18th day of April, A. 1)., 1921.

' RAY L. STOKELY. 

